Hakuouki  

 薄桜鬼

Upon learning that her father disappeared, a teenaged girl dresses as boy and travels to the city of Kyoto in hopes of finding him. On the first day in the city, she happens to witness a sword fight between some samurai and some demon warriors. Taken into custody by the samurai, she learns that they are the Shinsengumi, a group who knows her father and are very interested in learning why his hospital clinic burned down so mysteriously a month before. With no family or friends to turn to, she is forced to count on the dashing and handsome members of the Shinsengumi to further her search.